Recently, with the spread of smartphones and tablet PCs and activation of high-capacity multimedia communication, mobile traffic has significantly increased. Future mobile traffic is expected to increase by about twice current mobile traffic each year. Since most mobile traffic is transmitted through a base station (BS), communication service operators are being confronted with serious network load. To process increasing traffic, communication operators have installed networks and have hurried commercialization of next-generation mobile communication standard, such as mobile WiMAX or long term evolution (LTE), capable of efficiently processing large amounts of traffic. However, another solution is required to cope with greater amounts of traffic in the future.
D2D communication refers to decentralized communication technology for directly transmitting traffic between continuous nodes without using an infrastructure such as a BS. In a D2D communication environment, each node of a portable device, etc. searches for physically adjacent devices, configures a communication session, and transmits traffic. Since such D2D communication is being spotlighted as elementary technology of next-generation mobile communication after 4G due to its traffic overload solving ability by distributing traffic converging towards the BS. For this reason, a standardization institute such as 3rd generation partnership (3GPP) or institute of electrical and electronics engineers (IEEE) is establishing D2D communication standard based on LTE-advanced (LTE-A) or Wi-Fi and Qualcomm etc. have developed independent D2D communication technology.
D2D communication is expected not only to contribute to increased performance of a mobile communication system but also to create a new communication service. Further, an adjacency based social network service or a network game service can be supported. A connectivity problem of a device in a shadow area can be overcome using a D2D link as a relay. Thus, D2D technology is expected to provide new services in various fields.
In fact, D2D communication, such as infrared communication, ZigBee, radio frequency identification (RFID), and near field communication (NFC) based on RFID, has already been widely used. However, strictly speaking, it is difficult for these technologies to be classified as D2D communication for decentralizing traffic of a BS because they support only special communication purposes within a significantly limited distance (around 1 m).
While D2D communication has been described hereinabove, a D2D frame structure for efficiently performing D2D communication in a cellular network or a method for performing D2D communication has not been proposed in detail up to now.